This paper presents SNI, Interactions Navigational Diagram, as a UI representation model allowing to design a CUI in accordance with users requirements and to generate automatically a skeleton of the wished software, using model transformation. To do so, two model levels are proposed. The conceptual level (SNI) specifies the functional navigation in the software independently of any technical platform. The logical level describes the dynamic chaining and the detailed definition of UI components according to a particular development platform (GUI, WEB, Multimodal…). This paper presents these two model levels, their respective metamodels and the software tool "VisualSNI" allowing to build the SNI and to generate a mock-up in the JSF framework automatically.